The invention pertains generally to trailer suspension systems, in particular to load bearing single wheel suspension systems used on smaller utility or recreational trailers. Transport of trailers used for various purposes such as utility or recreational vehicles require the wheel and axle assembly to operate smoothly while transporting a wide range of loads or unloaded, such as an empty trailer.
Single or multiple axle trailers are prevalent in the market with one or more wheels on each side of the trailer frame. Other designs in the market have a single wheel mounted in the rear of the trailer near its center. The towing vehicle supports the trailer at two front attachment points so the trailer swings with the vehicle during turns. Such single wheel designs often have a single downwardly and rearwardly extending arm with the wheel carried at the lower end thereof. The upper end of the arm is attached to pivot on a vertical caster shaft to allow the wheel to follow the towing vehicle during turns without scrubbing on the ground.
A particular problem with this design is the possibility at highway speeds for wheel on a single wheel trailer to begin to oscillate from side to side on the caster shaft. This may occur with such speed and violence that the axle breaks or the tire on the wheel blows out, dropping the rim to the ground and potentially damaging the trailer and its load and endangering humans.
Many believe that proper alignment of the wheel center axis with the center axis of the mounting spindle has a direct bearing on the occurrence and amount of oscillation that can occur while traveling at highway speeds. Where this is the reason for this problem, the tolerance in this alignment is relatively small. Although manufacturers have the ability to control such tolerances, doing so is expensive, and other causes of this oscillation may exist as well. For example, replacing a worn wheel may change the alignment and convert a satisfactory wheel assembly to one that is prone to oscillation.
One currently available solution to this oscillation problem is a braking unit on the spindle assembly to dampen vibrations. Such solutions may reduce the damaging effects of the vibrations but include disadvantages of further maintenance of the brake system and added complexity and cost, while not sufficiently resolving the problem. The variety of trailer chassis designs and wheel sizes available in the market creates a large margin for error when tolerances for each complete system are tight, thus creating a challenge for aftermarket and replacement parts.
For these reasons, there is a need for a single wheel trailer suspension that will operate satisfactorily with a variety of trailer and hitch assemblies that is not susceptible to oscillation during towing at highway speeds.